RIGHT ANTERIOR PREFRONTAL CORTEX ACTIVATION DURING SEMANTIC MONITORING AND WORKING-MEMORY

Areas of the adult human brain used for semantic monitoring were ident ified using positron emission tomography. For a series of tasks, subje cts viewed a list of familiar English nouns and monitored the words fo r names of dangerous animals. The monitoring task used here also conta ined an instruction to keep track of the number or percentage of targe ts for report after the scan. Surface characteristics of the tasks suc h as stimulus rate, number of targets, and whether subjects were asked to count or estimate the number of targets were varied across multipl e conditions within and between subjects. A passive word viewing condi tion was used as the control in all subjects. Reliable activations wer e identified in anterior and dorsal right prefrontal cortex [Brodmann areas (BA) 9 and 10] and left extrastriate cortex. The right prefronta l cortical locations are similar to areas that have been activated dur ing many episodic memory tasks. This surprising finding led to a thoro ugh review of the literature for examples of other activations within 16-mm vector distance of this right prefrontal area. Activations in th e vicinity of right BA10 due to episodic memory retrieval, to various forms of working memory, and to miscellaneous tasks were found. The ri ght prefrontal activations in the current experiment and the additiona l working memory and miscellaneous tasks demonstrate that, although ri ght BA10 is routinely activated by episodic retrieval tasks, it is not uniquely activated by episodic retrieval tasks. (C) 1998 Academic Pre ss.